Any tips on how to get all of the grout out of those ridges on rough slate tiles?
I tried a grout bag my last project and it wouldn't flow for me so I threw it away and went back to the old "smear and spread" method. I find that I can't get it as clean as I want it. Those ridges just collect the grout and are impossible to clean !!!! Does grout release even work for this problem?
Sealer will help. All stone tile should be sealed first anyway.
Grout release will also help.
When grouting go slow and use a toothbrush as you clean up. I have never had a slate floor I couldn't get clean.
A grout bag has a slight learning-curve but it is easy. The grout must be a mixed slightly thinner than usual to keep it from coagulating in the narrows of the bag too soon.
Using a good (new) grout float is a key factor also. Try the gummed-rubber grout float.